ИСТИНА

Introduction: Galilean icy moons differ from most objects of the Solar System in several respects. Except of remarkably high reflectance in the optical [1] and microwave [2] spectrum, they exhibit anomalous polarization signatures of radar echoes [2], not typical for most planetary surfaces. Due to that, many studies address issues of their structure, composition and thermal regime. Disk-integrated and disk-resolved measurements in a broad wavelength range [3] provided information on the surface temperature and its changes over the diurnal cycle. The Submillimeter Wave Instrument (SWI) is a spectrometer and radiometer with two channels working in frequency bands around 600 and 1200 GHz. It will register the radio brightness temperatures of the icy surface at these frequencies. This will give a possibility to study the global structure of icy crust and tectonic and resurfacing processes. In the Jovian icy moons' crust, volume scattering should be expected to be relatively more significant, due to probably lower absorption in comparison to the lunar regolith. For the correct interpretation of microwave radiometry observational data, relevant radiative transfer models, adequately treating transport of the electromagnetic radiation in millimeter and submillimeter microwave bands, should be elaborated as well as the approaches for retrieval of the physical quantities of interest. In this study, thermal radiation of the icy moons' surfaces is simulated by numerical solution of the radiative transfer equation. A Bayesian retrieval procedure for thermal and electrical properties of the surface has been tested with the simulated radiometry data. The study is partially supported by the Max-Planck-Institut für Sonnensystemforschung. Support from Russian Science Foundation with the grant 17-77-20087 is also kindly acknowledged. References: [1] Buratti B.J. Application of a radiative transfer model to bright icy satellites. // Icarus. 1985. V.61. P.208-217. [2] Black G.J., Campbell D.B., Nicholson P.D. Icy Galilean satellites: Modeling radar reflectivities as a coherent backscatter effect. // Icarus. 2001. V.151. P.167-180. [3] Orton G.S., Spencer J.R., Travis L.D., et al. Galileo photopolarimeter-radiometer observations of Jupiter and the Galilean satellites. // Science. 1996. V.274. P.389-391.